This invention concerns industrial filters of a type designed to filter cutting fluids. These fluids are used in the machining of metal parts, such as engine blocks, manifolds, cylinder heads, etc. to cool and lubricate, and to carry off chips, etc. The cutting fluids are directed at the parts during machining, and in mass production installations are collected for filtration and reuse.
Large quantities of metal particles along with grit from grinding and other material, are typically generated which must be removed by the filter apparatus. In some operations such as honing, very fine metal particles are generated which tend to quickly clog the filter media, requiring increased filter capacity and/or reduced filter flow rates. The larger metal turnings sometimes cause tearing of the media. A type of filter apparatus widely used for this application comprises a tank into which the contaminated liquid is introduced and within which a media sheet material is advanced over a vacuum box. Liquid is drawn through the media sheet section overlying the vacuum box to be filtered.
The media and conveyor are indexed periodically to bring a fresh media section over the vacuum box.
A flight conveyor extending over the media is driven to assist in moving large quantities of filtered solids out of the tank.
Applicant has previously patented a method using such apparatus featuring a combination of a permanent and disposable sheet material filter media. See U.S. Pat. No. 5,624,579, issued on Apr. 29, 1997, which describes this filter.
If the metal particles could be removed from the liquid, the filter load could be greatly reduced, such that flow to the filter could be increased and, a smaller filter therefor used, and/or the indexing rate reduced.
This is particularly true where fine metal particles are present, such as with honing machines. These very fine particles are accompanied with oils which tend to be drawn to the metal particles, the oils tend to clog the filter media.
Magnetic separators have previously been devised which use permanently magnetized elements which attract ferromagnetic particles to remove the same from suspension in the liquid in a tank. Such separators have heretofore been separate from the primary filter, increasing the floor space required.
Magnetic separator elements have typically comprise an array of elongated permanently magnetized bars arranged side by side in a tank with intervening spaces through which the liquid is circulated. The metal particles are attracted to the magnetized bars, which are periodically scraped off, the scrapings collected by a conveyor removing the same from the tank.
Uniform circulation of liquid over the bars have been difficult to achieve, as the liquid tends to flow directly to a tank outlet, creating localized regions of higher and lower flow rates. Higher flow velocities tend to allow metal particles to escape the magnetic attraction of the bars and pass out of the separator.
Furthermore, scraping mechanisms heretofore employed have been bulky, using long power cylinders projecting to one side of the tank, and have not provided a particularly effective scraping action.
It is an object of the present invention to provide a filter method and apparatus of the type described which incorporates a magnetic separator to simplify and reduce the size of the combined apparatus.
It is a further object to provide a magnetic separator of improved performance.
It is yet another object to provide an improved scraper mechanism for a magnetic separator.